1. Field of the Invention
The present invention relates to a recording medium for reproducing images, which has a layer of photosensitive microcapsules that are cured or softened upon exposure to a radiation. The invention is also concerned with a method of reproducing images or making copies of a document, by utilizing a recording medium as indicated above.
2. Background of the Invention
There is known a recording medium which has a planar substrate coated with a layer of microcapsules each containing a radiation-curable photosensitive material and a chromogenic material. Images are reproduced according to varying hardness of the microcapsules in the local areas of the medium.
A recording medium of the type indicated above is indicated generally at 50 in FIG. 5. The recording medium 50 includes a planar substrate 51 coated with a developer layer 53, and a microcapsule layer 54 formed on the developer layer 53. The microcapsule layer 54 consists of a multiplicity of microcapsules 55. Each microcapsule 55 has a shell 57 encapsulating an internal liquid phase 59 which includes a radiation-curable composition and a chromogenic material. The developer layer 53 consists of a developer material which is capable of chemically reacting with the chromogenic material of the internal phase 59 of the microcapsules 55, and thereby cooperating with the chromogenic material to produce a color or colors.
Referring to FIGS. 6 and 7, there is illustrated a method by which images are reproduced on the recording medium 50. In the method, an original 63 bearing an image thereon is irradiated with a radiation produced by a light source 61. Due to imaged and non-imaged local areas of the original 63, the corresponding local areas of the microcapsule layer 54 are selectively exposed and remain unexposed to the radiation. The microcapsules 55a in the exposed local areas of the microcapsule layer 54 are cured and hardened, as indicated in FIG. 6. In the next step, the recording medium 50 is passed through a pressure nip between two presser rolls 65, 65 as indicated in FIG. 7 (wherein only one of the two presser rolls is shown), whereby the uncured microcapsules 55b in the unexposed local areas of the microcapsule layer 54 are ruptured. As a result, the chromogenic material comes out of the ruptured microcapsules 55b, and chemically reacts with the developer material of the developer layer 53. Thus, the images on the original 63 are reproduced on the recording medium 50, by imagewise exposing the microcapsule layer 54 to the radiation through the original 63.
Another known method of reproducing images employs two separate sheets. The first sheet has a microcapsule layer formed on a planar substrate, while the second sheet has a developer layer formed on a planar substrate. The microcapsule layer of the first sheet is imagewise exposed to a radiation in the same manner as described above, and the second sheet is superposed on the thus exposed first sheet. A pressure is applied to the superposed first and second sheets, to thereby rupture the uncured microcapsules and cause a chemical reaction between the chromogenic material of the ruptured microcapsules and the developer material of the developer layer of the second sheet, whereby the images on the original are reproduced.
The conventional imaging methods discussed above require a recording medium or sheet which is coated with a layer of a developing material which is capable of chemically reacting with a chromogenic material of the microcapsules. Thus, the conventional methods do not permit image reproduction on an ordinary sheet. The cost of the recording medium having both the microcapsule layer and the developer layer is considerably higher than an ordinary sheet of paper. Accordingly, the cost of image reproduction using this type of recording medium is considerably high. Further, the cost of image reproduction using two separate sheets as described above is also comparatively high.